I must respectfully disagree with the "hotter plug" advice. Changing heat ranges on plugs from oem is a risky proposition. A long time ago I put a hole in a piston in a racing engine doing this. The problem is that they can raise combustion temperature. Has to do with the size (height) of the plug and how quickly it dissipates heat. If you choose too hot, you can indeed bring the piston surface to beyond the melting point of the metal, at high loads or speeds. You have to get up pretty early in order to beat the designer at his game. I have relearned this lesson over and over. You really should stay with the OEM heat range. The solution to excessive oil/carbon might have nothing to do with the top end (how about rings....)
Benzmac: I'd be curious as to why you have a problem with the Platinum plugs? Thanks.